Michael,
Here is a start and I'm sure others will add to it. The 1316 head came from a
1275 and is the one you should use provided it checks out OK. The 295 was
really a small bore head, and as you noticed the valves are too small. Used to
be that everyone had to have the 12G940 head, but the 1316 can flow just as
good and the only difference is the air injection ports. Did you measure the
thickness of the head to determine that it was cut .068"? That's not a lot and
I wouldn't worry about it because it is only the final chamber volume that
will matter. You can correct for that during the other head work by
unshrouding and adjusting valve depth. More important is to look to see how
deep the valves are seated and then pull the valves and check the seat for
damage. If there are problems with the seats it would be cheaper to look for
another head, but you could install seat inserts or larger valves to correct
this.
To evaluate the cranks first bend a heavy piece of wire to insert in one of
the crank flange bolt holes, and ring it! In other words, suspend it and tap
it with a hammer on one of the C'weights. If you get a thud you can pitch it
in the trash, if it "Rings" you have a keeper and can evaluate the journals,
etc.
The block numbers don't mean much to me, but the first thing I would do is to
look inside for cylinder sleeves. Lots of blocks were sleeved, and normally
you don't want to start with one of those. They can't be bored reliably past
.020", and you don't know what kind of damage was corrected by sleeving.
Buying and replacing sleeves is expensive, and I would just find another
block.
John
Fogelsville, PA
--- On Tue, 1/12/10, Michael Rowe <mdrowe@optonline.net> wrote:
From: Michael Rowe <mdrowe@optonline.net>
Subject: [Spridgets] Choices - heads, cranks, and blocks
To: "Spridget Chat Group" <spridgets@autox.team.net>
Date: Tuesday, January 12, 2010, 2:49 PM
I have two 1275 heads from which to choose: One is fairly rusty but
cleanable, a newer version (sculpted surface, Vizard p170) with a standard
casting number 12G 295. It is apparently unmodified, with small valves,
although it looks like there may have been a little reduction in the guide
boss. I have not yet taken out the valves (no spring compressor), so it is
hard to tell.
The other is in good condition but apparently older (flat surface, Vizard
p169) with casting number 12G 1316, which I have not yet been able to find
described anywhere. It has much larger valves and has been shaved roughly
0.068". Dema Elgin says my cam (one step above Cooper S) should not use a
compression ratio greater than 9:1, so it is possible that this head is shaved
too much.
Similarly, I have two cranks, one rusty and one clean. Neither is obviously
modified from stock (crank journal 1.625"). Both have holes drilled through.
One is marked B1 and the other P1, the meaning of which I have not yet found.
And I have two blocks, both reasonably clean. Both are 12G 1279 with
miscellaneous other numbers (2 155 103MD, 1 184 10L), the meaning of which I
have not yet found. They do not look different to my inexperienced eye.
Any thoughts on the relative merits of any of these pieces to be modified as
necessary for a "medium" level of upgrade?
Michael Rowe
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